Arrangement adapted to suppress radio frequency currents on conductors



APT!I 1947. 1-1.0. ROOSENSTEIN 2,419,855

ARRANGEMENT ADAPTED To SUPPRESS RADIO FREQUENCY CURRENTS ON CONDUCTORS Filed Oct. 17, 1940 INVENTOR IMMS 0. RL?N$TEIN ATTORNEY Patented Apr. 29, 1947 ARRANGEMENT ADAPTED TO SUPPRESS RADIO FREQUENCY CURRENTS N CON- DUCTORS Hans Otto Roosenstein,

in the Attorney Gener Berlin, Germany; vested al of the United States Application October 17, 1940, Serial No. 361,564 In Germany June 22, 1939 3 Claims.

This invention relates to means to suppress the flow of radio frequency currents On conductors, especially of the so-called shell waves on the outer surface of cable shielding. Contradistinct to prior practice, according to this invention, to the said end, the conductor which is to be rid of radio frequency waves is built up of portions of dissimilar characteristic impedance, preferably of M4 length rather than by the aid of a short-circuit or rejector system, with the result that the radio frequency waves are gradually attenuated completely as a result of reflections produced at the points of discontinuity of the characteristic impedance. The general and broad principle underlying the invention shall now be explained in greater detail by reference to the appended drawing as applied to the feeding of an antenna S by way of a shielded line or cable L. If the outer shell of the line were simply free-ended, this outer surface, in the light of experience, would become excited; in other words, so-called shell waves would arise and these would exercise a harmful effect upon the antenna radiation. In order to avoid the said waves, the

outer sheath is composed of several pieces or portions A1, B1, A2, B2 of dissimilar wall thickness, and each of these possesses different characteristic impedance values. The length of these components is preferably equal to M4. Now,

if the assumption is made that at the juncture of connection points of the cable K itself there still flows a vanishingly small current I, it can be demonstrated that the current at point and the current at point Zn 2 I 4) while the current at point it follows that at point K flows a current equal to one-twenty-seventh that at point 3; in other words, the shell wave has dropped to /27. If, in line with what is being shown in the drawing, there is moreover used an antenna at the base of which only a small current intake is required, in other words, for instance, a 7\/2 antenna, it will be seen that also the shell wave amplitude at the base end of the antenna is extremely small. If the antenna currents at points 0 and a are as 10:1, it follows that the amplitude of the shell waves at point K is /z1o the amplitude at point 3. These shell waves may be taken to be negligible for practical purposes.

The invention is not confined to the suppression of shell waves, in fact, it may generally be used for the purpose Of suppressing radio frequency waves along conductors. If the length of the component parts is not made equal to M4, then the calculation is somewhat more complicated. However, the attenuation of shell waves also in this instance is practicable in the same Way as above described.

I claim:

1. An arrangement for suppressing the flow of radio frequency energy along a conductor in which said conductor is divided into a series of sections, each having a length equal to an odd multiple of a quarter of the operating wavelength, the outside diameter of said sections so varying that the surge impedance of each section so differs from that of adjacent sections that a maximum reflection of energy occurs at each junction between sections.

2. An arrangement for suppressing the flow of energy along the outer conductor of a concentric transmission line in which said outer conductor is divided into sections of different outside diameters such that the surge impedance of each section differs from that of adjacent sections, each having a length equal to an odd multiple of a quarter of the operating wavelength, the relationship between the impedances of adjacent sections being such as to cause a large reflection of energy at each junction between sections.

3. An arrangement for suppressing the flow of radio frequency energy along the outer conductor of a concentric transmission line in which said outer conductor i divided into sections of difierent diameter such that the surge impedance of each section differs from that of adjacent sec- UNITED STATES PATENTS tions whereby reflection of energy occurs at each Number Name Date junction between Sections, each section having a 2 Danenbach t length equal to an odd multiple, including unity, 2205874 Buschbeck Julie 1940 a quarter the length the Wanting Wave- 5 2 131,108 Lindenbladtjj jj Sept. 2'? 193a HANS OTTO ROOSENSTEIN' 1,859,390 Green May 24, 1932 2,236,102 Kolster Mar. 25, 1941 REFERENCES CITED 2,184,729 Bailey Dec, 26, 1939 The following references are of record in the 10 2,127,088 Percival et a1 Aug. 16, 1938 file of this patent: 2,038,240 Schelkunoff Apr. 21, 1936 

